Name Class Description TIMED_STATISTICS
application wait time
1
The total wait time (in microseconds) for waits that belong to the Application wait class

background checkpoints completed
8
Number of checkpoints completed by the background process. This statistic is incremented when the background process successfully advances the thread checkpoint.

background checkpoints started
8
Number of checkpoints started by the background process. This statistic can be larger than “background checkpoints completed” if a new checkpoint overrides an incomplete checkpoint or if a checkpoint is currently under way. This statistic includes only checkpoints of the redo thread. It does not include:
Individual file checkpoints for operations such as offline or begin backup
Foreground (user-requested) checkpoints (for example, performed by ALTER SYSTEM CHECKPOINT LOCAL statements)

background timeouts
128
This is a count of the times where a background process has set an alarm for itself and the alarm has timed out rather than the background process being posted by another process to do some work.

branch node splits
128
Number of times an index branch block was split because of the insertion of an additional value

buffer is not pinned count
72
Number of times a buffer was free when visited. Useful only for internal debugging purposes.

buffer is pinned count
72
Number of times a buffer was pinned when visited. Useful only for internal debugging purposes.

bytes received via SQL*Net from client
1
Total number of bytes received from the client over Oracle Net Services

bytes received via SQL*Net from dblink
1
Total number of bytes received from a database link over Oracle Net Services

bytes sent via SQL*Net to client
1
Total number of bytes sent to the client from the foreground processes

bytes sent via SQL*Net to dblink
1
Total number of bytes sent over a database link

calls to get snapshot scn: kcmgss
32
Number of times a snapshot system change number (SCN) was allocated. The SCN is allocated at the start of a transaction.

calls to kcmgas
128
Number of calls to routine kcmgas to get a new SCN

calls to kcmgcs
128
Number of calls to routine kcmgcs to get a current SCN

calls to kcmgrs
128
Number of calls to routine kcsgrs to get a recent SCN

change write time
8
Elapsed redo write time for changes made to CURRENT blocks in 10s of milliseconds.
Y
cleanouts and rollbacks – consistent read gets
128
Number of consistent gets that require both block rollbacks and block cleanouts.
See Also: “consistent gets”

cleanouts only – consistent read gets
128
Number of consistent gets that require only block cleanouts, no rollbacks.
See Also: “consistent gets”

commit cleanout failures: cannot pin
8
Total number of times a commit cleanout was performed but failed because the block could not be pinned

commit cleanout failures: hot backup in progress
8
Number of times Oracle attempted block cleanout at commit during hot backup. The image of the block must be logged before the buffer can be made dirty.

commit cleanout failures: write disabled
8
Number of times a cleanout block at commit was performed but the writes to the database had been temporarily disabled

commit cleanouts
8
Total number of times the cleanout block at commit function was performed

commit cleanouts successfully completed
8
Number of times the cleanout block at commit function completed successfully

commit nowait performed
1
The number of asynchronous commits that were actually performed. These commits did not wait for the commit redo to be flushed and be present on disk before returning.

commit nowait requested
1
The number of no-wait commit or asynchronous commit requests that were made either using SQL or the OCI transaction control API

Commit SCN cached
128
Number of times the system change number of a commit operation was cached

commit wait/nowait performed
1
The number of asynchronous/synchronous commits that were actually performed

commit wait/nowait requested
1
The number of no-wait or wait commits that were made either using SQL or the OCI transaction control API

commit wait performed
1
The number of synchronous commits that were actually performed. These commits waited for the commit redo to be flushed and be present on disk before returning.

commit wait requested
1
The number of waiting or synchronous commit requests that were made either using SQL or the OCI transaction control API

concurrency wait time
1
The total wait time (in microseconds) for waits that belong to the Concurrency wait class

consistent changes
8
Number of times a user process has applied rollback entries to perform a consistent read on the block
Work loads that produce a great deal of consistent changes can consume a great deal of resources. The value of this statistic should be small in relation to the “consistent gets” statistic.

consistent gets
8
Number of times a consistent read was requested for a block.
See Also: “consistent changes” and “session logical reads” statistics

consistent gets direct
8
Number of times a consistent read was requested for a block bypassing the buffer cache (for example, direct load operation). This is a subset of “consistent gets” statistics value.

consistent gets from cache
8
Number of times a consistent read was requested for a block from buffer cache. This is a subset of “consistent gets” statistics value.

CPU used by this session
1
Amount of CPU time (in 10s of milliseconds) used by a session from the time a user call starts until it ends. If a user call completes within 10 milliseconds, the start and end user-call time are the same for purposes of this statistics, and 0 milliseconds are added.
A similar problem can exist in the reporting by the operating system, especially on systems that suffer from many context switches.
Y
CPU used when call started
128
The CPU time used when the call is started
See Also: “CPU used by this session”
Y
CR blocks created
8
Number of CURRENT blocks cloned to create CR (consistent read) blocks. The most common reason for cloning is that the buffer is held in a incompatible mode.

current blocks converted for CR
8
Number CURRENT blocks converted to CR state

cursor authentications
128
Number of privilege checks conducted during execution of an operation

data blocks consistent reads – undo records applied
128
Number of undo records applied to data blocks that have been rolled back for consistent read purposes

db block changes
8
Closely related to “consistent changes”, this statistic counts the total number of changes that were part of an update or delete operation that were made to all blocks in the SGA. Such changes generate redo log entries and hence become permanent changes to the database if the transaction is committed.
This approximates total database work. It statistic indicates the rate at which buffers are being dirtied (on a per-transaction or per-second basis, for example).

db block gets
8
Number of times a CURRENT block was requested
See Also: “consistent gets”

db block gets direct
8
Number of times a CURRENT block was requested bypassing the buffer cache (for example, a direct load operation). This is a subset of “db block gets” statistics value.

db block gets from cache
8
Number of times a CURRENT block was requested from the buffer cache. This is a subset of “db block gets” statistics value.

DBWR buffers scanned
8
Total number of dirty and clean buffers Oracle looks at when scanning LRU sets for dirty buffers to clean. Divide by “DBWR lru scans” to find the average number of buffers scanned.

DBWR checkpoint buffers written
8
Number of buffers that were written for checkpoints

DBWR checkpoints
8
Number of times the DBWR was asked to scan the cache and write all blocks marked for a checkpoint or the end of recovery. This statistic is always larger than “background checkpoints completed”.

DBWR cross instance writes
40
Real Application Clusters only: Number of blocks written to satisfy a lock request from another instance

DBWR free buffers found
8
Number of clean buffers that DBWR found when it was requested to make free buffers. Divide by “DBWR make free requests” to find the average number of reusable buffers at the end of each LRU.

DBWR lru scans
8
Number of times that DBWR scans the LRU queue looking for buffers to write. This count includes scans to fill a batch being written for another purpose (such as a checkpoint). This statistic is always greater than or equal to “DBWR make free requests”.

DBWR make free requests
8
Number of requests to DBWR to make some free buffers for the LRU

DBWR revisited being-written buffer
8
Number of times that DBWR tried to save a buffer for writing and found that it was already in the write batch. This statistic measures the amount of “useless” work that DBWR had to do in trying to fill the batch.
Many sources contribute to a write batch. If the same buffer from different sources is considered for adding to the write batch, then all but the first attempt will be “useless” because the buffer is already marked as being written.

DBWR summed scan depth
8
The current scan depth (number of buffers examined by DBWR) is added to this statistic every time DBWR scans the LRU for dirty buffers. Divide by “DBWR lru scans” to find the average scan depth.

DBWR transaction table writes
8
Number of rollback segment headers written by DBWR. This statistic indicates how many “hot” buffers were written, causing a user process to wait while the write completed.

DBWR undo block writes
8
Number of rollback segment blocks written by DBWR

DDL statements parallelized
32
Number of DDL statements that were executed in parallel

deferred (CURRENT) block cleanout applications
128
Number of times cleanout records are deferred, piggyback with changes, always current get

DFO trees parallelized
32
Number of times a serial execution plan was converted to a parallel plan

dirty buffers inspected
8
Number of dirty buffers found by the user process while it is looking for a buffer to reuse

DML statements parallelized
32
Number of DML statements that were executed in parallel

enqueue conversions
4
Total number of conversions of the state of table or row lock

enqueue deadlocks
4
Total number of deadlocks between table or row locks in different sessions

enqueue releases
4
Total number of table or row locks released

enqueue requests
4
Total number of table or row locks acquired

enqueue timeouts
4
Total number of table and row locks (acquired and converted) that timed out before they could complete

enqueue waits
4
Total number of waits that occurred during an enqueue convert or get because the enqueue get was deferred

exchange deadlocks
8
Number of times that a process detected a potential deadlock when exchanging two buffers and raised an internal, restartable error. Index scans are the only operations that perform exchanges.

execute count
64
Total number of calls (user and recursive) that executed SQL statements

fbda woken up
128
Number of times the flashback data archive background process was woken up to do archiving

file io wait time
1
Total time spent in wait (in microseconds) for I/O to datafiles, excluding the service time for such I/O. This is cumulative for all I/Os for all datafiles. The service time for one I/O operation is estimated as the minimum time spent in the I/O call seen so far. This service time is subtracted from the time spent in each I/O call to get the wait time for that I/O.

flash cache eviction: buffer pinned
8
Database Smart Flash Cache buffer is invalidated due to object or range reuse, and so on. The Database Flash Cache Buffer was in use at the time of eviction.

flash cache eviction: invalidated
8
Database Smart Flash Cache buffer is invalidated due to object or range reuse, and so on. The Database Smart Flash Cache buffer was not in use at the time of eviction.

flash cache insert skip: corrupt
8
In-memory buffer was skipped for insertion into the Database Smart Flash Cache because the buffer was corrupted

flash cache insert skip: exists
8
In-memory buffer was skipped for insertion into the Database Smart Flash Cache because it was already in the flash cache

flash cache insert skip: modification
8
In-memory buffer was skipped for insertion into the Database Smart Flash Cache because it was being modified

flash cache insert skip: not current
8
In-memory buffer was skipped for insertion into the Database Smart Flash Cache because it was not current

flash cache insert skip: not useful
8
In-memory buffer was skipped for insertion into the Database Smart Flash Cache because the type of buffer was not useful to keep

flash cache inserts
8
Total number of in-memory buffers inserted into the Database Smart Flash Cache

flashback log write bytes
2
Total size in bytes of flashback database data written by RVWR to flashback database logs

flashback log writes
2
Total number of writes by RVWR to flashback database logs

foreground propagated tracked transactions
128
Number of transactions modifying tables enabled for flashback data archive which were archived by a foreground process

free buffer inspected
8
Number of buffers skipped over from the end of an LRU queue to find a reusable buffer. The difference between this statistic and “dirty buffers inspected” is the number of buffers that could not be used because they had a user, a waiter, or were being read or written, or because they were busy or needed to be written after rapid aging out.

free buffer requested
8
Number of times a reusable buffer or a free buffer was requested to create or load a block

gc read wait failures
40
A read wait is when a CR server waits for a disk read to complete before serving a block to another instance. This statistic displays the number of times a read wait ended in failure, that is, after waiting it was unable to serve a block.

gc read wait time
40
A read wait is when a CR server waits for a disk read to complete before serving a block to another instance. This statistic displays the total time spent waiting for disk reads (in centiseconds). The average time waited is “gc read wait time” / “gc read waits.”

gc read wait timeouts
40
A read wait is when a CR server waits for a disk read to complete before serving a block to another instance. This statistic displays the number of times a read wait timed out, that is, the disk read did not complete in time, so the wait was aborted.

gc read waits
40
The number of times a CR server waited for a disk read, and then successfully served a block

global cache cr block receive time
40
Total amount of time foreground processes waited for a CR block to be sent through the interconnect. This statistic divided by “global cache cr blocks received” = time waited per block.

global enqueue CPU used by this session
32
Amount of CPU time (in 10s of milliseconds) used by synchronous and asynchronous global enqueue activity in a session from the time a user call starts until it ends. If a user call completes within 10 milliseconds, the start and end user-call time are the same for purposes of this statistics, and 0 milliseconds are added.

hot buffers moved to head of LRU
8
When a hot buffer reaches the tail of its replacement list, Oracle moves it back to the head of the list to keep it from being reused. This statistic counts such moves.

in call idle wait time
1
The total wait time (in microseconds) for waits that belong to the Idle wait class.
See Also: “non-idle wait count” and “non-idle wait time”

instance recovery database freeze count
32
Number of times the database is frozen during instance recovery

kcmccs called get current scn
32
Number of times the kernel got the CURRENT SCN when there was a need to casually confirm the SCN

kcmgss read scn without going to DLM
32
Number of times the kernel got a snapshot SCN without going to the distributed lock manager (DLM)

kcmgss waited for batching
32
Number of times a database process is blocked waiting for a snapshot SCN

large tracked transactions
128
For tables tracked by flashback data archive, the number of transactions modifying rows in those tables which are large in terms of size or number of changes

leaf node splits
128
Number of times an index leaf node was split because of the insertion of an additional value

lob reads
8
Number of LOB API read operations performed in the session/system. A single LOB API read may correspond to multiple physical/logical disk block reads.

lob writes
8
Number of LOB API write operations performed in the session/system. A single LOB API write may correspond to multiple physical/logical disk block writes.

lob writes unaligned
8
Number of LOB API write operations whose start offset or buffer size is not aligned to the internal chunk size of the LOB. Writes aligned to chunk boundaries are the most efficient write operations. The internal chunk size of a LOB is available through the LOB API (for example, DBMS_LOB.GETCHUNKSIZE()).

logons cumulative
1
Total number of logons since the instance started. Useful only in V$SYSSTAT. It gives an instance overview of all processes that logged on.

logons current
1
Total number of current logons. Useful only in V$SYSSTAT.

messages received
128
Number of messages sent and received between background processes

messages sent
128
Number of messages sent and received between background processes

native hash arithmetic execute
64
Number of hash operations performed using native arithmetic rather than Oracle NUMBERs

native hash arithmetic fail
64
Number of has operations performed using native arithmetic that failed, requiring the hash operation to be performed with Oracle NUMBERs

next scns gotten without going to DLM
32
Number of system change numbers obtained without going to the distributed lock manager or server

no buffer to keep pinned count
72
Number of times a visit to a buffer attempted, but the buffer was not found where expected. Like “buffer is not pinned count” and “buffer is pinned count”, this statistic is useful only for internal debugging purposes.

non-idle wait count
1
The total number of waits performed with wait events that were not part of the Idle wait class.
See Also: “in call idle wait time” and “non-idle wait time”

non-idle wait time
1
The total wait time (in microseconds) for waits that do not belong to the Idle wait class.
See Also: “in call idle wait time” and “non-idle wait count”

OLAP Paging Manager Cache Hit
64
The number of times a requested page is found in the OLAP page pool. Use this statistic in conjunction with OLAP Paging Manager Cache Miss to determine the OLAP page pool efficiency ratio.

OLAP Paging Manager Cache Miss
64
The number of times a requested page is not found in the OLAP page pool. Use this statistic in conjunction with OLAP Paging Manager Cache Hit to determine the OLAP page pool efficiency ratio.

OLAP Paging Manager New Page
64
The number of newly-created pages in the OLAP page pool that have not yet been written to the workspace LOB

OLAP Paging Manager Cache Write
64
The number of times the OLAP paging manager writes to a page in the OLAP page pool.

OLAP Session Cache Hit
64
The number of times the requested, dynamically-aggregated value of an AW object, was found in the OLAP session cache.

OLAP Session Cache Miss
64
The number of times the requested, dynamically-aggregated value of an AW object, was not found in the OLAP session cache.

OLAP Aggregate Function Calc
64
The number of times the AGGREGATE function computes a parent value based on the values of its children.

OLAP Aggregate Function Precompute
64
The number of times the AGGREGATE function is to compute a value and finds it precomputed in the cube.

OLAP Aggregate Function Logical NA
64
The number of times an AGGREGATE function evaluates to a logical NA value. This could be because the AGGINDEX is on and the composite tuple does not exist.

OLAP Paging Manager Pool Size
64
Size, in bytes, of the OLAP page pool allocated to a session and the sum of all OLAP page pools in the system.

OLAP Import Rows Pushed
64
The number of OLAP import rows pushed. This statistic refers to the number of rows encountered from a source cursor and is useful during cube build operations.

OLAP Import Rows Loaded
64
The number of OLAP import rows loaded. This statistic provides the number of rows of the source cursor that are actually loaded into an Analytic Workspace (AW).
The difference between the OLAP Import Rows Pushed and OLAP Import Rows Loaded provides the number of rejected rows.

OLAP Row Source Rows Processed
64
The number of rows processed by the OLAP row source
.
OLAP Engine Calls
64
The total number of OLAP transactions executed within the session. This value provides a general indication of the level of OLAP activity in the session.

OLAP Temp Segments
64
The number of OLAP pages stored in temporary segments for analytic workspaces

OLAP Temp Segments Read
64
The number of times data was read from a temporary segment and not from the OLAP page pool

OLAP Perm LOB Read
64
The number of times data was read from the table where the AW is stored. These are permanent LOB reads.

OLAP Paging Manager Cache Changed Page
64
The number of times the OLAP page pool is changed for any attached AW.

OLAP Fast Limit
64
The number of times an OLAP table function issues a fast limit

OLAP GID Limit
64
The number of times an OLAP table function issues a Cube Grouping ID (CGID) limit. Typically, this type of limit occurs for query rewrite transformations that resolve to a cube organized materialized view.

OLAP INHIER Limit
64
The number of times an OLAP table function issues an in-hierarchy limit. This type of limit can occur when you use cube dimension hierarchy views.

OLAP Full Limit
64
The number of times an OLAP table function issues a full limit

OLAP Custom Member Limit
64
The number of times an OLAP table function issues a custom member limit

OLAP Row Id Limit
64
The number of times an OLAP table function issues a row Id limit.

OLAP Limit Time
64
The total time taken by all the OLAP Limit operations that were performed during the last call to the OLAP table function

OLAP Row Load Time
64
The total time spent loading rows into an AW during cube build and OLAP SQL import operations.
Use this statistic along with the OLAP engine elapsed time to measure time spent running OLAP engine routines that involve loading data into AWs from a SQL source.
This statistic has the following levels of precision:
Low precision timer
This captures the elapsed time of the entire fetch phase of the SQL cursor that is being loaded into AWs. It includes the SQL execution time that occurs during a fetch operation from a source cursor and time taken by the OLAP engine to populate AWs.
High precision timer
This captures the elapsed time, excluding the SQL processing of the cursor being loaded. It records the time spent in the OLAP engine only.
Default timer precision:
This is based on the STATISTIC_LEVEL parameter. If the low precision is used, then STATISTICS_LEVEL is TYPICAL. The high precision timer is used when STATISTIC_LEVEL is set to ALL. No timing is captured when STATISTICS_LEVEL is BASIC.

OLAP Unique Key Attribute Limit
64
The number of times an OLAP table function issues a unique key attribute limit

opened cursors cumulative
1
In V$SYSSTAT: Total number of cursors opened since the instance started.
In V$SESSTAT: Total number of cursors opened since the start of the session.

opened cursors current
1
Total number of current open cursors

opens of replaced files
8
Total number of files that had to be reopened because they were no longer in the process file cache

opens requiring cache replacement
8
Total number of file opens that caused a current file in the process file cache to be closed

OS All other sleep time
16
Time spent sleeping for reasons other than misses in the data segment (see “OS Data page fault sleep time”), kernel page faults (see “OS Kernel page fault sleep time”), or misses in the text segment (see “OS Text page fault sleep time”). An example of such a reason is expiration of quanta.

OS Chars read and written
16
Number of bytes read and written

OS CPU Qt wait time
1
The time a session spends on the CPU run queue (in microseconds), waiting to get the CPU to run

OS Data page fault sleep time
16
Time spent sleeping due to misses in the data segment

OS Input blocks
16
Number of read I/Os

OS Involuntary context switches
16
Number of context switches that were enforced by the operating system

OS Minor page faults
16
Number of page faults that did not result in an actual I/O

OS Other system trap CPU time
16
Total amount of time to process system traps (as distinct from system calls)

OS Output blocks
16
Number of write I/Os

OS Process heap size
16
Size of area in memory allocated by the process. Typically this represents memory obtained by way of malloc().

OS Process stack size
16
Size of the process stack segment

OS Signals received
16
Number of signals received

OS Swaps
16
Number of swap pages

OS System call CPU time
16
Total amount of time spent executing in system mode

OS System calls
16
Number of system calls

OS Text page fault sleep time
16
Time spent sleeping due to misses in the text segment

OS User level CPU time
16
Total amount of time spent executing in user mode

OS Voluntary context switches
16
Number of voluntary context switches (for example, when a process gives up the CPU by a SLEEP() system call)

Parallel operations downgraded 1 to 25 pct
32
Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers

Parallel operations downgraded 25 to 50 pct
32
Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers

Parallel operations downgraded 50 to 75 pct
32
Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers

Parallel operations downgraded 75 to 99 pct
32
Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers

Parallel operations downgraded to serial
32
Number of times parallel execution was requested but execution was serial because of insufficient parallel execution servers

Parallel operations not downgraded
32
Number of times parallel execution was executed at the requested degree of parallelism

parse count (hard)
64
Total number of parse calls (real parses). A hard parse is a very expensive operation in terms of memory use, because it requires Oracle to allocate a workheap and other memory structures and then build a parse tree.

parse count (describe)
64
Total number of parse calls on a describe cursor. This operation is a less expensive than a hard parse and more expensive than a soft parse.

parse count (total)
64
Total number of parse calls (hard, soft, and describe). A soft parse is a check on an object already in the shared pool, to verify that the permissions on the underlying object have not changed.

parse time cpu
64
Total CPU time used for parsing (hard and soft) in 10s of milliseconds
Y
parse time elapsed
64
Total elapsed time for parsing, in 10s of milliseconds. Subtract “parse time cpu” from the this statistic to determine the total waiting time for parse resources.
Y
physical read bytes
8
Total size in bytes of all disk reads by application activity (and not other instance activity) only.

physical read flash cache hits
8
Total number of reads from flash cache instead of disk

physical read IO requests
8
Number of read requests for application activity (mainly buffer cache and direct load operation) which read one or more database blocks per request. This is a subset of “physical read total IO requests” statistic.

physical read requests optimized
8
Number of read requests that read one or more database blocks from the Database Smart Flash Cache or the Exadata Smart Flash Cache.

physical read total bytes
8
Total size in bytes of disk reads by all database instance activity including application reads, backup and recovery, and other utilities. The difference between this value and “physical read bytes” gives the total read size in bytes by non-application workload.

physical read total IO requests
8
Number of read requests which read one or more database blocks for all instance activity including application, backup and recovery, and other utilities. The difference between this value and “physical read total multi block requests” gives the total number of single block read requests.

physical read total multi block requests
8
Total number of Oracle instance read requests which read in two or more database blocks per request for all instance activity including application, backup and recovery, and other utilities.

physical reads
8
Total number of data blocks read from disk. This value can be greater than the value of “physical reads direct” plus “physical reads cache” as reads into process private buffers also included in this statistic.

physical reads cache
8
Total number of data blocks read from disk into the buffer cache. This is a subset of “physical reads” statistic.

physical reads cache prefetch
8
Number of contiguous and noncontiguous blocks that were prefetched.

physical reads direct
8
Number of reads directly from disk, bypassing the buffer cache. For example, in high bandwidth, data-intensive operations such as parallel query, reads of disk blocks bypass the buffer cache to maximize transfer rates and to prevent the premature aging of shared data blocks resident in the buffer cache.

physical reads direct (lob)
8
Number of buffers that were read directly for LOBs

physical reads direct temporary tablespace
8
Number of buffers that were read directly from temporary tablespaces

physical reads for flashback new
8
Number of blocks read for newing (that is, preparing a data block for a completely new change) blocks while flashback database is enabled

physical reads prefetch warmup
8
Number of data blocks that were read from the disk during the automatic prewarming of the buffer cache.

physical write bytes
8
Total size in bytes of all disk writes from the database application activity (and not other kinds of instance activity).

physical write IO requests
8
Number of write requests for application activity (mainly buffer cache and direct load operation) which wrote one or more database blocks per request.

physical write total bytes
8
Total size in bytes of all disk writes for the database instance including application activity, backup and recovery, and other utilities. The difference between this value and “physical write bytes” gives the total write size in bytes by non-application workload.

physical write total IO requests
8
Number of write requests which wrote one or more database blocks from all instance activity including application activity, backup and recovery, and other utilities. The difference between this stat and “physical write total multi block requests” gives the number of single block write requests.

physical write total multi block requests
8
Total number of Oracle instance write requests which wrote two or more blocks per request to the disk for all instance activity including application activity, recovery and backup, and other utilities.

physical writes
8
Total number of data blocks written to disk. This statistics value equals the sum of “physical writes direct” and “physical writes from cache” values.

physical writes direct
8
Number of writes directly to disk, bypassing the buffer cache (as in a direct load operation)

physical writes direct (lob)
8
Number of buffers that were directly written for LOBs

physical writes direct temporary tablespace
8
Number of buffers that were directly written for temporary tablespaces

physical writes from cache
8
Total number of data blocks written to disk from the buffer cache. This is a subset of “physical writes” statistic.

physical writes non checkpoint
8
Number of times a buffer is written for reasons other than advancement of the checkpoint. Used as a metric for determining the I/O overhead imposed by setting the FAST_START_IO_TARGET parameter to limit recovery I/Os. (Note that FAST_START_IO_TARGET is a deprecated parameter.) Essentially this statistic measures the number of writes that would have occurred had there been no checkpointing. Subtracting this value from “physical writes” gives the extra I/O for checkpointing.

pinned buffers inspected
8
Number of times a user process, when scanning the tail of the replacement list looking for a buffer to reuse, encountered a cold buffer that was pinned or had a waiter that was about to pin it. This occurrence is uncommon, because a cold buffer should not be pinned very often.

prefetched blocks aged out before use
8
Number of contiguous and noncontiguous blocks that were prefetched but aged out before use

process last non-idle time
128
The last time this process executed
Y
PX local messages recv’d
32
Number of local messages received for parallel execution within the instance local to the current session

PX local messages sent
32
Number of local messages sent for parallel execution within the instance local to the current session

PX remote messages recv’d
32
Number of remote messages received for parallel execution within the instance local to the current session

PX remote messages sent
32
Number of remote messages sent for parallel execution within the instance local to the current session

queries parallelized
32
Number of SELECT statements executed in parallel

recovery array read time
8
Elapsed time of I/O during recovery

recovery array reads
8
Number of reads performed during recovery

recovery blocks read
8
Number of blocks read during recovery

recovery blocks read for lost write detection
8
Number of blocks read for lost write checks during recovery.

recovery blocks skipped lost write checks
8
Number of Block Read Records that skipped the lost write check during recovery.

recursive calls
1
Number of recursive calls generated at both the user and system level. Oracle maintains tables used for internal processing. When Oracle needs to make a change to these tables, it internally generates an internal SQL statement, which in turn generates a recursive call.

recursive cpu usage
1
Total CPU time used by non-user calls (recursive calls). Subtract this value from “CPU used by this session” to determine how much CPU time was used by the user calls.

redo blocks checksummed by FG (exclusive)
2
Number of exclusive redo blocks that were checksummed by the generating foreground processes. An exclusive redo block is the one whose entire redo content belongs to a single redo entry.

redo blocks checksummed by LGWR
2
Number of redo blocks that were checksummed by the LGWR.

redo blocks written
2
Total number of redo blocks written. This statistic divided by “redo writes” equals number of blocks per write.

redo buffer allocation retries
2
Total number of retries necessary to allocate space in the redo buffer. Retries are needed either because the redo writer has fallen behind or because an event such as a log switch is occurring.

redo entries
2
Number of times a redo entry is copied into the redo log buffer

redo entries for lost write detection
2
Number of times a Block Read Record is copied into the log buffer.

redo log space requests
2
Number of times the active log file is full and Oracle must wait for disk space to be allocated for the redo log entries. Such space is created by performing a log switch.
Log files that are small in relation to the size of the SGA or the commit rate of the work load can cause problems. When the log switch occurs, Oracle must ensure that all committed dirty buffers are written to disk before switching to a new log file. If you have a large SGA full of dirty buffers and small redo log files, a log switch must wait for DBWR to write dirty buffers to disk before continuing.
Also examine the log file space and log file space switch wait events in V$SESSION_WAIT

redo log space wait time
2
Total time waited in centiseconds for available space in the redo log buffer. See also”redo log space requests”
Y
redo ordering marks
2
Number of times that a system change number was allocated to force a redo record to have a higher SCN than a record generated in another thread using the same block

redo size
2
Total amount of redo generated in bytes

redo size for lost write detection
2
Total amount of Block Read Records generated in bytes.

redo synch time
8
Elapsed time of all “redo synch writes” calls in 10s of milliseconds
Y
redo synch writes
8
Number of times the redo is forced to disk, usually for a transaction commit. The log buffer is a circular buffer that LGWR periodically flushes. Usually, redo that is generated and copied into the log buffer need not be flushed out to disk immediately.

redo wastage
2
Number of bytes wasted because redo blocks needed to be written before they are completely full. Early writing may be needed to commit transactions, to be able to write a database buffer, or to switch logs.

redo write broadcast ack count
2
Number of times a commit broadcast acknowledgment has not been received by the time when the corresponding log write is completed. This is only for Oracle RAC.

redo write broadcast ack time
2
Total amount of the latency associated with broadcast on commit beyond the latency of the log write (in microseconds). This is only for Oracle RAC.
Y
redo write time
2
Total elapsed time of the write from the redo log buffer to the current redo log file in 10s of milliseconds
Y
redo writes
2
Total number of writes by LGWR to the redo log files. “redo blocks written” divided by this statistic equals the number of blocks per write

remote instance undo block writes
40
Number of times this instance wrote a rollback segment so that another instance could read it

remote instance undo header writes
40
Number of times this instance wrote a undo header block so that another instance could read it

scheduler wait time
1
The total wait time (in microseconds) for waits that belong to the Scheduler wait class

serializable aborts
1
Number of times a SQL statement in a serializable isolation level had to abort

session connect time
1
The connect time for the session in 10s of milliseconds. This value is useful only in V$SESSTAT. It is the wall clock time since the logon to this session occurred.
Y
session cursor cache count
64
Total number of cursors cached. This statistic is incremented only if SESSION_CACHED_CURSORS > 0. This statistic is the most useful in V$SESSTAT. If the value for this statistic in V$SESSTAT is close to the setting of the SESSION_CACHED_CURSORS parameter, the value of the parameter should be increased.

session cursor cache hits
64
Number of hits in the session cursor cache. A hit means that the SQL (including recursive SQL) or PL/SQL statement did not have to be reparsed. Subtract this statistic from “parse count (total)” to determine the real number of parses that occurred.

session logical reads
1
The sum of “db block gets” plus “consistent gets”. This includes logical reads of database blocks from either the buffer cache or process private memory.

session pga memory
1
Current PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

session pga memory max
1
Peak PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

session stored procedure space
1
Amount of memory this session is using for stored procedures

session uga memory
1
Current UGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

session uga memory max
1
Peak UGA size for a session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

shared hash latch upgrades – no wait
8
A shared hash latch upgrade is when a hash latch is upgraded from shared mode to exclusive mode. This statistic displays the number of times the upgrade completed immediately.

shared hash latch upgrades – wait
8
A shared hash latch upgrade is when a hash latch is upgraded from shared mode to exclusive mode. This statistics displays the number of times the upgrade did not complete immediately.

slave propagated tracked transactions
128
Number of transactions modifying tables enabled for flashback data archive which were archived by a slave process

sorts (disk)
64
Number of sort operations that required at least one disk write
Sorts that require I/O to disk are quite resource intensive. Try increasing the size of the initialization parameter SORT_AREA_SIZE. For more information, see “SORT_AREA_SIZE”.

sorts (memory)
64
Number of sort operations that were performed completely in memory and did not require any disk writes
You cannot do much better than memory sorts, except maybe no sorts at all. Sorting is usually caused by selection criteria specifications within table join SQL operations.

sorts (rows)
64
Total number of rows sorted

SQL*Net roundtrips to/from client
1
Total number of Oracle Net Services messages sent to and received from the client

SQL*Net roundtrips to/from dblink
1
Total number of Oracle Net Services messages sent over and received from a database link

summed dirty queue length
8
The sum of the dirty LRU queue length after every write request. Divide by write requests to get the average queue length after write completion.

switch current to new buffer
8
Number of times the CURRENT block moved to a different buffer, leaving a CR block in the original buffer

table fetch by rowid
64
Number of rows that are fetched using a ROWID (usually recovered from an index)
This occurrence of table scans usually indicates either non-optimal queries or tables without indexes. Therefore, this statistic should increase as you optimize queries and provide indexes in the application.

table fetch continued row
64
Number of times a chained or migrated row is encountered during a fetch
Retrieving rows that span more than one block increases the logical I/O by a factor that corresponds to the number of blocks than need to be accessed. Exporting and re-importing may eliminate this problem. Evaluate the settings for the storage parameters PCTFREE and PCTUSED. This problem cannot be fixed if rows are larger than database blocks (for example, if the LONG data type is used and the rows are extremely large).

table scan blocks gotten
64
During scanning operations, each row is retrieved sequentially by Oracle. This statistic counts the number of blocks encountered during the scan.
This statistic tells you the number of database blocks that you had to get from the buffer cache for the purpose of scanning. Compare this value with the value of “consistent gets” to determine how much of the consistent read activity can be attributed to scanning.

table scan rows gotten
64
Number of rows that are processed during scanning operations

table scans (cache partitions)
64
Number of range scans performed on tables that have the CACHE option enabled

transaction rollbacks
128
Number of transactions being successfully rolled back

transaction tables consistent read rollbacks
128
Number of times rollback segment headers are rolled back to create consistent read blocks

transaction tables consistent reads – undo records applied
128
Number of undo records applied to transaction tables that have been rolled back for consistent read purposes

Unnecessary process cleanup for SCN batching
32
Total number of times that the process cleanup was performed unnecessarily because the session or process did not get the next batched SCN. The next batched SCN went to another session instead.

user calls
1
Number of user calls such as login, parse, fetch, or execute
When determining activity, the ratio of user calls to RPI calls, give you an indication of how much internal work gets generated because of the type of requests the user is sending to Oracle.

user commits
1
Number of user commits. When a user commits a transaction, the redo generated that reflects the changes made to database blocks must be written to disk. Commits often represent the closest thing to a user transaction rate.

user I/O wait time
1
The total wait time (in microseconds) for waits that belong to the User I/O wait class

user rollbacks
1
Number of times users manually issue the ROLLBACK statement or an error occurs during a user’s transactions

very large tracked transactions
128
For tables tracked by flashback data archive, number of transactions modifying those tables which are very large in terms of size or number of changes

write clones created in background
8
Number of times a background or foreground process clones a CURRENT buffer that is being written. The clone becomes the new, accessible CURRENT buffer, leaving the original buffer (now the clone) to complete writing.

write clones created in foreground
8
Number of times a background or foreground process clones a CURRENT buffer that is being written. The clone becomes the new, accessible CURRENT buffer, leaving the original buffer (now the clone) to complete writing.